The semiconductor integrated circuit industry has experienced rapid growth in the past several decades. Technological advances in semiconductor materials and design have produced increasingly smaller and more complex circuits. These material and design advances have been made possible as the technologies related to processing and manufacturing have also undergone technical advances. In the course of semiconductor evolution, the number of interconnected devices per unit of area has increased as the size of the smallest component that can be reliably created has decreased.
The pursuit of smaller feature size has required a number of technological changes, including changes to lithography systems. Lithography systems include a light or radiation source that is filtered, directed, and focused in order to better transmit a pattern from a mask onto a wafer. One trend of recent years has been to adjust the wavelength of light used to expose semiconductor wafers. Another trend has been to use phase-shifting masks. However, despite these improvements in lithography systems, the current technology has not been entirely satisfactory.
Aspects of the figures in the present disclosure are best understood from the following detailed description when read in connection with the figures.